In the present study the innervation of the anal sac and the anal canal of 44 cats was examined by lightmicroscopical techniques as well as by histochemical, immunohistochemical and electron-microscopical methods. These methods had been chosen to detect all nerval structures in this body area and to show the quality of the different nerve fibers. The anal sac of the cat possesses sebaceous glands and apocrine secreting tubular glands. Both types of glands also exist in the caudal part of the anal canal, the Zona cutanea, together with hairs. Free nerve endings are situated in the connective tissue of the anal sac and duct and additionally in the epithelium of the duct. It could be shown, that the apocrine tubular glands were surrounded by a dense network of cholinergic and adrenergic fibers. However, the specific role of the so-called Scheiteldrüse, which possesses similarities with an eccrine sweat gland, was discussed. In the connective tissue of the anal sac wall, small lamellar corpuscles and Pacinian corpuscles are rare. The thin muscle layer of the external anal spincter muscle, which covers the anal sac, is supplied with motor end plates and muscle spindles. The distribution of nerve fibers and nerve endings in the duct wall is much higher than in the sac wall, because of the duct´s regulatory function in releasing the anal sac secret. Free nerve endings supply the epithelium of the Zona columnaris and the connective tissue of all three zones of the anal canal. In the Zona cutanea, free nerve endings encircle the hair bulbs. Small lamellar corpuscles are situated in the connective tissue of the Zona cutanea, Pacinian corpuscles lie in the connective tissue of the Zona intermedia and cutanea and, more often, in the connective tissue between the external anal spincter muscle. The apocrine sweat glands of the Zona cutanea, which are very well developed, were surrounded by cholinergic and adrenergic fibers. The shortest distance, which was measured between nerve fibers and myoepithelial cells of the glands, was 0.7 µm, the same as in the anal sac wall. In these fibers small clear vesicles and large dense core vesicles were detected. Around the sebaceous glands of the Zona cutanea there run cholinergic nerve fibers. The special function of the well developed glands of the anal canal was discussed concerning the results of the innervation of these glands.